Sift flour, and soda together. In a large bowl combine butter, sugar, egg and vanilla. If using an electric mixer approximately 2 minutes at med. speed. Gradually add sour cream and flour to the mixture slowly. Beat an additional 2 minutes. Refrigerate to chill for 1-2 hours. Lightly flour surface, roll out dough, cut with cookie cutters and place on a greased cookie sheet and bake for 10-12 minutes. Can apply frosting after they cool or sugar after they are removed from the oven. Enjoy.